Dark Radiation Isocurvature from Cosmological Phase Transitions

Tuesday 12 Nov 2024, 10:00 → 12:00 Asia/Shanghai

online

Abstract: Cosmological first-order phase transitions are typically associated with physics beyond the Standard Model, and thus of great theoretical and observational interest. In this talk, I will show that a broad class of non-thermal first-order phase transitions could generate distinct large-scale isocurvature in dark radiation that can be observable in the CMB. We derive constraints on Delta N_eff from phase transitions based on CMB+BAO data, which can be much stronger than that from adiabatic initial conditions. I will also demonstrate that since perturbations of dark radiation have a non-Gaussian origin, searches for non-Gaussianity in the CMB could also place a stringent bound on Delta N_eff.

Biography:

Peizhi Du is currently a postdoc at Rutgers University since 2022. He received his PhD from University of Maryland in 2019 and then moved to Stony Brook University for his first postdoc position (2019-2022). His research focuses on theoretical particle physics and cosmology, including dark matter direct detection and probing new physics in astrophysics and cosmology.